Trimming device for airplanes



July 12, 1932. T M N 1,867,162

TRIMMING DEVICE FOR AIRPLANES Filed March 4, 1951 s Sheets-Sheet 1 TRIMMING DEVICE FOR AIRPLANES Filed March 4, 1951 s, Sheets-Sheet 2 July 12, 1932. T, P, LEAMAN 1,867,162

TRIMMING DEVICE FOR AIRPLANES Filed March 4, 1931 .5 Sheets-Sheet I5 Patented July 12, 1932 UNITED STATES PATENT OFFICE THOMAS P, LEE-MN, F EEMPS'IEAD, NEW YORK, ASSIGNOR 1'0 AMIPHIIBIONS, INCL, OF

GARDEN CITY, NEW YORK, A CORPORATION OF NEW YORK TBIHMING DEVICE FOR AIRPLANES Application filed Hatch 4, 1931. Serial No. 520,020.

This invention relates to airplanes and more particularly to a trimming device therer for, and has for an object to provide an improved means for improving longitudinal a stability control (rotation about a transverse horizontal axis Y) of an airplane in flight.

It is also an object of the invention to provide improved directional stability control (rotation about a vertical axis Z through the center of gravity) of an airplane.

Another object of the invention is to secure both of these controls in the same mechanism.

Still another objectof the invention is to provide mounting means for two control members whereby the two controls may be si multaneously operated, and means whereby they may be individually adjusted with relation to each other.

With the foregoing and other objects in view the invention consists in certain novel features of construction, combinations and arrangements of parts as will be more fully disclosed in connection with-the accompany- 5 ing drawings. y

In these drawings:

Fig. 1 is a side elevation of a conventionalflying boat showing my invention applied thereto; I

Fig. 2 is an end view on an enlarged scale looking forward;

Fig. 3 isa side elevation of one of my improved trimming air-foils or fins;

Fi 4 is a transverse section thereof sub I as views looking aft showing difierent effects which may be secured with this improved trimming device.

lnthe drawings the hull of the conventional flying boat is indicated at 12 with any suitdt able typeof wings 13 and the motor r4 operating a propeller 15. Spaced rearwardly from the hull is the usual horizontal abilizer 16 associated with the elevators 17 pivoted to swing about horizontal pivotedmountings 18, with the usual upright stationary fin or vertical stabilizer 19, and the vertical steering rudder 20 mounted to swing about an upright axis in the usual manner.

As is. well known with change of loading the center of gravity will shift and therefore in order to maintain stability of the airplane in flight this change must be compensated for, but in'place of the usual adjustment on the horizontal stabilizer for the purpose of maintaining longitudinal stability of the airplane in flight with change of airplane loading I have provided an improved means operable from the pilots cock-pit for maintainingthis stability and also providing direc-- tional stability or control of rotation about a vertical axis through the center of gravity. I accomplish this by providing at a suitable distance. either fore or aft of the center ofgravity of the airplane trimming'fins or airfoils which are inclined to the horizontal and extend laterally in opposite directions. The most convenient and efl'ective position for mounting them is in the tail of the airplane and Ihave shown them in the drawings, as located under the horizontal stabilizer 16, and on opposite sides of the vertical stabilizer or fin 19. These two trimming fins or airfoils are shown at 21 and 22, and each is mounted so as to turn about its longitudinal axis. It will be noted from Fig. 2, which is a view looln'ng forward, that each fin or I airfoilv is pivotally mounted on a support 23, and are inclined upwardly in opposite directions from their connections to the vertical stabilizer fin 19 to a point where they are connected to the underside of the horizontal stabilizer 16. It will thus be evident that the two trimming members 21 and 22 extend laterally in opposite directions from the vertical central plane of the airplane and are inclined upwardly from a horizontal transverse line passing through their connections to the vertical stabilizer fin 19. These trimming elements 21 and 22 may be mounted on any suitable supports, but n order to simplify con- 3% struction and decrease the number of arts they are preferably mounted on the inc ined struts usually provided between the undersides of the horizontal stabilizer 16 and the .loWer edge portion of the vertical stabilizer 19. Thus the fins 21 and 22 are preferably mounted to turn about these struts which are indicated diagrammatically at 23, or they may themselves form the struts'and thus take the place of the usual struts, but in either case they are mounted to turn about longitudinal axes. 7

.These trimmingfins or airfoils 21 and 22 may be of any desired cross section but it is preferable that they be made of airfoil section to reduce drag and render them more .23. These elements 24 therefore tend to turn these members in one direction about their axes, that shown being in a direction to depress or lower their trailing edges 26. They may be shifted in the opposite direction by a cable control leading to the pilots cock-pit.

Thus each one of these trimming elements is provided with an arm'27 to which is connecteda cable 28 running over suitable guides 29 connected to bell cranks 30 pivoted at 31 to suitable supports 32.. These bell cranks are connected y rod 33 on which is an'arm 34 connected by a push rod 35 connected at 36 to a lever 37 pivoted at 38. This lever has a hand grip 39 mounting for telescoping sliding engagement on the lever 37 and provided with a' slot 40 for passage of a curved rack 41.

sgring 42'tends to shift the grip '39 upar ly, and engage the lower walls of the slot with the notches 43 in the rack and thus lock the lever in different adjusted ositions. This lever will be located in the pi ots cock pit, and it will be evident that by merely depressing the grip 39 the handle will be unlocked to permit shiftin of the lever either forwardly or backward y, and thus adjust the fins or airfoils 21 and 22 on their pivotal mountings. This will adjust the angular relation of these fins both to the horizontal and vertical lanes to secure the effects presently to be d scribed. In each of the cables 28 .is mounted a turn buckle 44 for adjusting the lengths of the cables and therefore the relative positions of the members 21 and 22 may be independently adjusted with respect to each other. It will thus be evident that by manipulating the lever37 the two fins or air-foils 21 and 22 aresimultaneously shifted about their pivotal mountingsin the same direction and through the same angle, but by manipulating the turn buckles 44 the angular D desired, and the whole frame covered with g suitable covering material such as fabric.

It will be evident that if the center of I gravity is shifted rearwardly then this may be compensated for to maintain longitudinal stability by means tending to lift the tail or depressing the nose of the aircraft. Thus 'as indicated in Fig. 8 the lever37 has been the vertical components 48 of the forces 49 of the fins are equal and positive. That is,

upwardly and of course in the .same direction, while the horizontal components 50 are equal and in op osite directions and toward each other or in card. The horizontal components therefore neutralize each other, but the vertical components being in the same direction tend to lift the tail.

If the center of gravity is shifted forward- 1y then by manipulating the lever 37 in the opposite direction the trailing edges 36 may be raised as indicated in' Fig. 9. In this view the trailing edges were lowered equal amounts to give equal angles of attack, but it will be evident that thevertieal compo nents 51 of the forces 52 are now downwardly but still in the same direction, while the horizontal com onents 53 are equal and in opposite directions but outwardly or outboard. Thus the horizontal components neutralize each other, but the vertical components work to ether to depress the tail;

It will be evi ent that dueto the inclination of the fins or airfoils 21and 22 they are u capable ofexerting a force which has both a horizontal and a vertical component. They therefore can be used not only for main-v taining lon itudinal stability of the airlane in flig twith change in airplane loadmg as illustrated in Figs. 8. and 9, but they may also be used for directional stability control, that is, rotation about the vertical axis through the center gravity of the air- 7 plane. For this control the two fins or airfoils are moved in opposite directions, that. is, the trailing edge of one is depressed or lowered and the other raised. This can be used to compensate for the effect of the spiral slip stream from the propeller on the tail fin or vertical stabilizer. Thus the effect of turn buckles 44 one of the members 21 or 22 may have its trailing edge raised and the other depressed so that both horizontal components are in the same direction and help each other to overcome this effect on the tail fin. Thus, in Fig. 10 the trailing edge 26 of the member 22 has been raised, while the trailing edge of member 21 has been depressed equal angles. Therefore, their horizontal components 54 are equal and in the same direction and to the left while the vertical components 55 are in opposite directions. In Fig. 11 elements 21 and 22 have been adjusted to different angles. Thus the trailing edge of element 22 has been raised while the trailing edge of element 21 has been depressed, but to a smaller angle than the element 22 has been raised. Thus both the vertical and horizontal components 56 and 57 are less than the vertical and horizontal components 58 and 59 of the member 22, but the horizontal components 57 and 59 are in the same direction while the vertical components 56 and 58 are in opposite directions All of these different effects and other eil'ects'can be secured by proper manipulation of the turn buckles 4:4 and the lever 37.

This device is also effective to provide controllability of the airplane in a spin. Thus because members 21 and 22 are inclined at an angle between the vertical and horizontal their effect or reaction from the air has horizontal components as well as a vertical component, as above described, which may produce in a spin a lifting force on the tail combined with a turning movement about the rollin axis of the airplane, thus tending to turn the nose of the airplane downward and toward the inside of the s in. This is a very nnportant feature as giving control in a spin where ordlnary elevators have no effect because in such a spin they are moving laterally and edgewise.

Having thus set forth the nature of my invention, what I claim is:

1. In an airplane having a tail portion including vertical and horizontal stabilizers, a fin extending between the vertical and horizontal stabilizers on each side of the vertical stabilizer, and each fin being inclined at an angle between the vertical and horizontal, means mounting each fin to turn about its longitudinal axis, and means for adjusting the positions of the fins.

2. In an airplane having atail portion includin vertical and horizontal stabilizers a pair of fins arranged one on each side of the vertical stabilizer and extending laterally and inclined'upwardly in opposite directions about an inclined axis, and means for adiusting the positions of the fins about said axes.

3. In an airplane having a tail portion including vertical and horizontal stabilizers, a fin extending between the vertical and horizontal stabilizers on each side-of the vertical stabilizer, and each fin being inclined at an angle between the vertical and horizontal, means mounting each fin to turn about an inclined longitudinal axis, means for simultaneously shiftin the fins about said axes, and means for shi ting the fins independently of each other.

4. In an airplane having a tail portion including vertical and horizontal stabilizers, a pair of fins arranged one on each side of the vertical stabilizer and extending laterally and inclined upwardly in opposite directions therefrom, means mounting each fin to turn about an inclined axis, means for simultane vously turning said fins about their axes, and

means for turning the fins independently of each other.

5. In an airplane havin a tail portion including vertical and horizontal stabilizers, inclined struts extending between the horizontal and vertical stabilizers on opposite sides of the latter and inclined in opposite directions, trimming fins mounted to turn about said struts, and means for adjusting the positions of the fins and retaining them in adjusted positions.

In testimony whereof I aflix my signature.

THOMAS P. LEAMAN.

therefrom, means mounting each fin to turn i lot 

